1. Field
The present invention relates generally to transceivers. More specifically, the present invention relates to transmitter to receiver rejection based on impedance balancing within a transceiver, feed forward cancellation within a transceiver, or both.
2. Background
As will be appreciated by a person having ordinary skill in the art, a wireless device may be able to simultaneously transmit and receive data on two frequency channels. A duplexer may be configured to route an RF input signal from an antenna to a receiver and to route a transmit signal from a transmitter to the antenna. Duplexers, which may provide isolation between a transmitter and a receiver sharing a single antenna, may perform both transmit filtering and receive filtering. More specifically, a duplexer may provide stop-band attenuation (e.g., approximately 50 dB) in a receive band (i.e., to strongly attenuate signals from extraneous sources in the receive frequency band) and stop-band attenuation (e.g., approximately 50 dB) in a transmit band, so that transmit signals do not leak into and saturate a receive chain. In the absence of such a duplexer, a conventional transceiver may not provide adequate performance.
Typically, a duplexer is commonly the largest and most costly component in a transceiver. Existing multi band/mode cellular devices use discrete duplexers, power amplifiers, and dedicated low-noise amplifier inputs for each radio frequency band, and sometimes more. With the number of bands increasing, this has proven to be costly. An integrated solution, which can use a single duplexer, power amplifier, and a low-noise amplifier (LNA) is desirable to reduce size and cost. A need exists for methods, systems, and devices for balancing impedances within a transceiver, feedforward cancellation within a receiver, or both, to provide adequate transmitter to receiver rejection.